Different types of filters

Is this part of an assignment set by your teacher at school or college ?

 

WW

It was for an assignment for a college class.

So why do you and your fellow students ask us to complete your assignments in the Black & White forum? Was it your instructor's idea? Or have you all now lost points for not noticing that these questions are mostly not about black and white photography?

Moderator Comment:

 

If these students are from the same class, then all is adequately explained in the link which I posted in a previous thread, when responding to comments about the nature of this recent spate of similarly styled questions.

 

Now - for general information here is a summary:

 

The information summarized here is a result of my many questions being answered the Students in various threads. It has been asked if the Teacher contacted Photo.net prior to suggesting to the Students to post questions: to my knowledge - no he did not. There is nothing in the Terms of Use and User Guidelines to suggest he should be bound so to do.

 

I understand that the Instructor asked the students to seek opinions from Photo.net Members and, I believe he specified the Black and White Forum to post the questions, obviously a mistake specifying B&W Forum, probably an innocent mistake of not understanding how our Forums operate: as I understand the course is mainly about Black and White Photography.

 

I further understand that is is NOT the intent that our members complete the assignments for the students, nor have I interpreted their questions to assume that: rather a Presentation is to be made by the Students after they have sifted and interpreted the many responses.

 

The intent of asking the Students to identify these questions as a school assignment is two-fold:

 

> firstly so that the threads, if better suited, may be moved to 'Beginner Forum' or 'Casual Photo Conversations Forum' and

 

> secondly, (perhaps more importantly), Members have full disclosure as to the reason for the Opening Post and thereby may craft their responses accordingly. Of course one always chooses to which threads one makes a comment.

 

Additionally, and for Members' general information, I have had received (a couple) of comments via PM regarding these Opening Posts, both with a similar theme that "we" are doing the Students work for them, so for absolute clarity, that is not so - if you like the Students have been charged to seek information and opinions from talented and experienced Photographers as first source martial from which they then compile and complete their assignment as a Presentation. Another way of looking at it is that the Students are interviewing 'us'.

 

I would encourage (and have encouraged) the Students to engage in the conversation beyond their opening post. Some have and by doing so have reaped more benefit.

 

That Photo.net Membership was chosen to be a research tank is a compliment for all of us.

 

This has been posted as a Moderator Comment for clarification, information and perhaps as guidance: please remember that comments on Moderation are not permitted on forum threads.

 

William

In case anyone has been persuaded by q.g's flat-earther denial of the existence of complementary colours.

 

Here are three subtractive primary (Yellow, Cyan, Magenta) filters overlaid.

You'll see that any two of these filters overlaid leave their common additive primary (Red, Green or Blue) to pass through.

However, where all three are superimposed, all colours are equally absorbed, leaving neutral grey.

 

This can be thought of in several ways: Cyan cancelling Red, Magenta cancelling Green, Yellow cancelling Blue, or the reverse of any of those combinations.

 

Thus the concept of complementary colours is seen absolutely to practically work, and indeed is the very basis of integral tri-pack reversal film technology. Not to mention every colour-printing process yet invented.

 

Here's a colour wheel showing the entire rainbow along with the complementary colours at 180 degrees opposite.

No, there is no single electromagnetic frequency that can stimulate the sensation of a magenta colour, but that's totally irrelevant. Because what's being perceived by the eye and brain is effectively a modulation of electromagnetic frequencies. In the same way that audio information can modulate an RF frequency.

 

We can't have an 'inverse' or complementary RF frequency, but we can very much have an anti-phase audio modulation.

In case anyone is interested, noone disputed or denied the existence of complementary colours.

 

For people interested in the physics of filtering, there are no complementary colours in the spectrum of light we are filtering. There are in the tricolour model of vision and image capture.

Given the right filters, you can filter out, say, green using either a red or a blue filter. That would make complementary colous red and blue both the complementary colour of green. You filter out magenta using a green filter, because magenta does not exist in the spectrum other than as a mix of red and blue. So use a filter (any filter) that does not transmit both red and blue (or either red or blue) and you will no longer see magenta. Et cetera.

Edited December 6, 2020 by William Michael

In case anyone has been persuaded by q.g's flat-earther denial of the existence of complementary colours.

 

Here are three subtractive primary (Yellow, Cyan, Magenta) filters overlaid.

[ATTACH=full]1367168[/ATTACH]

You'll see that any two of these filters overlaid leave their common additive primary (Red, Green or Blue) to pass through.

However, where all three are superimposed, all colours are equally absorbed, leaving neutral grey.

 

This can be thought of in several ways: Cyan cancelling Red, Magenta cancelling Green, Yellow cancelling Blue, or the reverse of any of those combinations.

 

Thus the concept of complementary colours is seen absolutely to practically work, and indeed is the very basis of integral tri-pack reversal film technology. Not to mention every colour-printing process yet invented.

 

Here's a colour wheel showing the entire rainbow along with the complementary colours at 180 degrees opposite.

[ATTACH=full]1367171[/ATTACH]

No, there is no single electromagnetic frequency that can stimulate the sensation of a magenta colour, but that's totally irrelevant. Because what's being perceived by the eye and brain is effectively a modulation of electromagnetic frequencies. In the same way that audio information can modulate an RF frequency.

 

We can't have an 'inverse' or complementary RF frequency, but we can very much have an anti-phase audio modulation.

So is the eye receiving a combined frequency, separate frequency, or what? So does white light goes through a yellow filter and you get a single frequency? Then does it go through blue and you get green frequency or two frequencies that the eye sees and the brain combines???

Edited December 6, 2020 by William Michael

Why not? The more the merrier:

Complimentary colors

Yellow to Blue - I think you're very nice

Blue to Yellow - thank you very much

So is the eye receiving a combined frequency, separate frequency, or what?

Separate frequencies or bands of frequencies in most cases.

 

Most naturally occuring pigments and dyes absorb across wide bands. The key word here is 'absorb'. Most common filters work by absorbing bands of frequencies, leaving those that pass as their characteristic colour.

 

Thus a common Y2(K) or CP yellow filter absorbs blue, leaving great chunks of light in the red and green parts of the spectrum to pass through. Add a magenta filter into the light path - thereby absorbing the green part of the yellow light - and you're left with red.

 

Same with the cyan filter that absorbs red, and the magenta filter that absorbs green.

 

However, if you start with the true primaries - red, green or blue - then any other colour of filter will absorb most of what passes through that filter.

 

Monochromatic light, reflectors and absorbers (allowing light of only one frequency or very narrow range of frequencies) is quite rare in nature and stands apart as needing special treatment and discussion.

Edited December 6, 2020 by rodeo_joe|1

In case anyone is interested

 

Colour is a concept q.g. It is not an innate property of a certain part of the EM spectrum. Therefore it needs to be dealt with conceptually.

 

noone disputed or denied the existence of complementary colours.

Except for you by claiming that a red or green filter must be the complement of blue because they absorb it.

 

That's the misleading nonsense.

 

A denial of complementary colours shows a complete incomprehension of the way that colour vision works, and of every method of photographic colour capture yet invented.

Edited December 6, 2020 by William Michael

Moderator Note: A general comment: If this conversation does not continue with-OUT the personal mud slinging insults: then it will not continue at all. This thread has been edited and some insults have been removed.

 

William

Edited December 6, 2020 by William Michael

Short answer, you use Red; Orange to deepen / darken skies and make clouds Pop! Yellow and Green are used to brighten foliage. Green is often used to make skin look healthier. Blue will brighten a dark sky. Of course you should experiment and make your own choices. Polarizers are used to see through or enhance glare on water surfaces and glass as well as manage reflections on metal. ND filters allow much slower shutter speeds in daylight for motion blur.

A UV filter cuts through distance haze.

I have difficulty seeing distance haze. I have trawled through tutorials that show with & without haze, and apparently the difference is obvious, but to me they look alike. I do see that the UV filter tones down the powerful turquoise-blue in sunny skies, making the photo appear not-so-sunny after all, but I'm not sure that is adding realism.

 

It bugs me that I cannot see what the experts claim is obvious. Is it just me?

I have difficulty seeing distance haze. I have trawled through tutorials that show with & without haze, and apparently the difference is obvious, but to me they look alike. I do see that the UV filter tones down the powerful turquoise-blue in sunny skies, making the photo appear not-so-sunny after all, but I'm not sure that is adding realism.

 

It bugs me that I cannot see what the experts claim is obvious. Is it just me?

No. The effect is very small. It needs a lot of UV and long distances to become visible at all.